There is a need to prevent seizures, galling, and heat generation due to metallic contact with molds in plastic working such as forging, extruding, and press working for metallic materials. For adapting to this need, films, oils, soaps and the like that have excellent lubricity have been used since a longtime ago. Above all, treatment with a zinc phosphate-based chemical conversion coating film and a soap-based lubricant (hereinafter, also referred to as bonder-lube treatment) has been often used, which is particularly excellent in workability and highly versatile.
However, high environmental loads have been a problem with the bonder-lube treatment. In the zinc phosphate-based chemical conversion treatment, the material to be treated is dissolved in the treatment liquid, thereby forming a by-product (sludge) with a phosphoric acid, and producing a large amount of industrial wastes. Moreover, in the bonder-lube treatment, effluents containing large amounts of heavy metals and effluent soaps are generated, thus requiring effluent treatment and treatment as industrial wastes. In recent years, new treatment methods of providing lubricity just by applying a water-based surface treatment agent to a metallic material and drying the agent have been developed in order to solve the problems as mentioned previously.
As such a technique, Patent Literature 1 discloses a technique of containing a water-soluble inorganic salt and a wax, etc. dissolved or dispersed in water.
Patent Literature 2 discloses a technique that relates to a lubricating composition for plastic working, containing a synthetic resin, a water-soluble inorganic salt, and water.
Patent Literature 3 discloses a technique that relates to a lubricant for plastic working, obtained by dispersing or dissolving, in water, 10 to 30% of a water-soluble inorganic salt, 5 to 30% of an organometallic salt, 10 to 84.5% of an alkaline-earth metal salt, and as a solid dispersant, 0.5 to 30% of a product of a reaction between a copolymer of α-olefin and maleic anhydride and N,N-dialkylaminoalkylamine.
Patent Literature 4 discloses a technique for a water-based lubricant composition for plastic working, containing a water-soluble polymer compound, an inorganic metal salt, and water.